The present invention relates to a pickup control device for an optical disk drive, and, more particularly, the invention relates to a control system and the saving of electricity in writing or reading information on or from a rotating optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the operation of focusing a laser beam on the optical disk (hereinafter abbreviated as xe2x80x9cfocusing operationxe2x80x9d) and a tracking servo system for controlling the operation of tracing an information storing track (hereinafter abbreviated as xe2x80x9ctrackxe2x80x9d) of the optical disk (hereinafter the tracing operation is abbreviated as xe2x80x9ctracking operationxe2x80x9d).
In recent years, under the circumstance that the rotational velocity of an optical disk increases in operating an optical disk drive, the increase of the data processing speed in the operation of the pickup of the optical disk drive is also required. However, when the data processing speed is increased, the consumption of electricity increases in the focus servo system and the tracking servo system for the control of the operation of the pickup, and, when these servo systems comprises digital processing circuits, the frequency of a clock pulse for operating the digital processing circuits increases, which also causes the increase of the consumption of electricity.
Hereinafter a conventional pickup control device for an optical disk drive is described on reference to FIG. 3 which is a block diagram showing the structure of the conventional pickup control device. In FIG. 3, a spindle motor 102 rotates an optical disk 100. A pickup 101 writes information on the optical disk 100 or reads information from the optical disk 100. An error signal detector 103 detects a focus error signal from the output signal of the pickup 101. A signal amplifier 104 amplifies the focus error signal. A driving circuit 106 receives the amplified signal through a compensating arithmetic unit 105, and operates the pickup 101 based on the received signal. The above structure forms a focus servo system.
On the other hand, a position detector 107 detects a track position (of a disk 100) where the pickup 101 is located. A gain selector 108 adjusts the loop gain for the focus servo system by controlling the signal amplifier 104 based on the signal on the track position where the pickup 101 is located, which (i.e., the signal) is generated by the position detector 107.
In general, the superficial fluctuation of the optical disk 100 is smaller at the inner tracks of the optical disk 100 comparing with the superficial fluctuation at the outer tracks of the optical disk 100. Therefore, when the pickup 101 is located at one of the inner tracks of the optical disk 100, the loop gain for the focus servo system is adjusted to a smaller value comparing with the loop gain in the occasion that the pickup 101 is located at one of the outer tracks of the optical disk 100.
The position detector 107, for detecting the track position where the pickup 101 is located, is formed, for instance, in such a manner that a reflecting portion is formed on the pickup 101, and a light emitted from a light emitter (not illustrated) is reflected by the reflecting portion of the pickup 101, and the reflected light is received by a light sensor (not illustrated), or, the position detector 107 is formed, for instance, in such a manner that track numbers are stored in advance on the optical disk 100 (i.e., formatted), and the stored track numbers are read by the pickup 101 in the occasion of the operation of writing or reading.
Based on the track position where the pickup 101 is located, which is detected by either of the above methods, the gain selector 108 controls the signal amplifier 104 in such a manner as to optimize the loop gain for the focus servo system.
The operation of a tracking servo system is performed in a manner similar to the above description on the focus servo system.
However, in the conventional pickup control device described in the above, a light emitter, light sensor and the like, which are exclusively used for detecting the track position where the pickup is located, are needed, which causes the increase of the consumption of electricity and the cost of the optical disk drive having the above conventional pickup control device. Also, in the conventional pickup control device having the structure of detecting the track position where the pickup is located by reading stored track numbers, the effective saving of electricity is not realized because it takes time before the tracking servo system becomes stable for reading the stored track numbers rightly after switching on the optical disk drive, such that the saving of electricity in this method is also insufficient.
The object of the present invention is to address the conventional problems and to provide a pickup control device for an optical disk drive, which enables the saving of electricity and cost in the optical disk drive.
For realizing the above object, the pickup control device of the present invention has the following structure. That is, in an optical disk drive which performs the operation of writing or reading information on or from an optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the focusing operation of the pickup and a tracking servo system for controlling the tracking operation of the pickup, a pickup control device for the optical disk drive in the present invention comprises,
(a) a first control system which comprises an angular velocity detector for detecting the angular velocity of the optical disk, and controls the optical disk based on the angular velocity detected by the angular velocity detector in such a manner that the optical disk enters into the state of rotation at a predetermined constant angular velocity, and
(b) a second control system which comprises a linear velocity detector for detecting the linear velocity of the optical disk at the track position of the optical disk where the pickup is located, and controls the linear velocity in such a manner that the linear velocity enters into the state of a predetermined constant linear velocity,
wherein the first control system and the second control system are alternatively operated in such a manner that the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on the linear velocity detected by the linear velocity detector of the second control system when the optical disk is rotated under the control of the first control system, and, the loop gains for at least one of the focus servo system and the tracking servo system are adjusted based on the angular velocity detected by the angular velocity detector of the first control system when the optical disk is rotated under the control of the second control system.
In the above structure of the pickup control device in the present invention, the operation of the pickup of the optical disk drive is optimally performed by utilizing the signal on the track position where the pickup is located, which (i.e., the signal) is generated by the angular velocity detector and the linear velocity detector which (i.e., both detectors) are also used for controlling the rotational velocity of the optical disk, without installing an additional unit comprising various component parts for detecting the track position where the pickup is located.
Also, for realizing the above object, the pickup control device of the present invention has the following structure. That is, in an optical disk drive which performs the operation of writing or reading information on or from an optical disk with the pickup of the optical disk drive comprising a focus servo system for controlling the focusing operation of the pickup and a tracking servo system for controlling the tracking operation of the pickup, a pickup control device for the optical disk drive in the present invention comprises,
(a) a first control system which comprises an angular velocity detector for detecting the angular velocity of the optical disk, and controls the optical disk based on the angular velocity detected by the angular velocity detector in such a manner that the optical disk enters into the state of rotation at a predetermined constant angular velocity, and
(b) a second control system which comprises a linear velocity detector for detecting the linear velocity of the optical disk at the track position of the optical disk where the pickup is located, and controls the linear velocity in such a manner that the linear velocity enters into the state of a predetermined constant linear velocity,
and at least one of the focus servo system and the tracking servo system have respective digital processing circuits,
wherein the first control system and the second control system are alternatively operated in such a manner that at least one of the sampling rate for operating the digital processing circuit of the focus servo system and the sampling rate for operating the digital processing circuit of the tracking servo system are determined based on the angular velocity detected by the angular velocity detector of the first control system when the optical disk is rotated under the control of the second control system.
In the above structure of the present invention, the optimal operation of the digital processing circuits is performed by utilizing the signal on the rotational velocity of the optical disk at the position where the pickup is located, which (i.e., the signal) is generated by the angular velocity detector and the linear velocity detector which (i.e., both detectors) are also used for controlling the rotational velocity of the optical disk, without installing an additional unit comprising various component parts for detecting the track position where the pickup is located.
As a result, the effective saving of electricity and cost in the optical disk drive having the above pickup control device of the present invention is realized.